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Marine Ecology Progress Series

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MEPS 602:63-76 (2018)  -  DOI:

Impact of nitrogen chemical form on the isotope signature and toxicity of a marine dinoflagellate

C. Taylor Armstrong1, Deana L. Erdner2, James W. McClelland2, Marta P. Sanderson1, Donald M. Anderson3, Christopher J. Gobler4, Juliette L. Smith1,*

1Virginia Institute of Marine Science, College of William & Mary, Gloucester Point, VA 23062, USA
2Marine Science Institute, University of Texas, Port Aransas, TX 78373, USA
3Woods Hole Oceanographic Institution, Woods Hole, MA 02543, USA
4Stony Brook University, Stony Brook, NY 11794, USA
*Corresponding author:

ABSTRACT: Stable isotopes are used to identify and track nitrogen (N) sources to water bodies and thus can be used to ascertain the N source(s) used by the phytoplankton in those systems. To focus this tool for a particular harmful algal species, however, the fundamental patterns of N isotope fractionation by that organism must first be understood. While literature is available describing N isotope fractionation by diatoms and coccolithophores, data are lacking regarding dinoflagellates. Here we investigated the effects of N chemical form on isotope fractionation (Δ) and toxin content using isolates of the dinoflagellate Alexandrium catenella in single-N and mixed-N experiments. Growth of A. catenella exclusively on nitrate (NO3-), ammonium (NH4+), or urea resulted in Δ of 2.7 ± 1.4, 29 ± 9.3, or 0.3 ± 0.1‰, respectively, with the lowest cellular toxicity reported during urea utilization. Cells initially utilized NH4+ and urea when exposed to mixed-N medium and only utilized NO3- after NH4+ decreased below 2 to 4 µM. This pattern of N preference was similar across all N treatments, suggesting that there is no effect of preconditioning on N chemical preference by A. catenella. In NO3-- and urea-rich environments, the δ15N of A. catenella would resemble the source(s) of N utilized, supporting this tool’s utility as a tracer of N source(s) facilitating bloom formation, but caution is advisable in NH4+-rich environments, where the large Δ value could lead to misinterpretation of the signal.

KEY WORDS:Alexandrium catenella · Dinoflagellates · Harmful algal blooms · Nitrogen · Saxitoxin · Stable nitrogen isotope

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Cite this article as: Armstrong CT, Erdner DL, McClelland JW, Sanderson MP, Anderson DM, Gobler CJ, Smith JL (2018) Impact of nitrogen chemical form on the isotope signature and toxicity of a marine dinoflagellate. Mar Ecol Prog Ser 602:63-76.

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